1. Field of the Invention
The present invention relates to a tape guide for a magnetic tape cartridge and/or tape drive, and more particularly to a tape guide which provides a fixed guide for one edge of a magnetic tape and a spring biased guide for an opposite edge of the tape.
2. Discussion of the Related Art
It is important that a magnetic tape handling device, such as a magnetic tape cartridge and/or drive, provide a reliable tape path on which a magnetic tape may be transported past a magnetic write/read head. This is especially true when a large number of narrow tracks are recorded on the tape, thereby requiring the head to follow the same path during playback that it followed during recording. When the playback path differs from the recording path, there can be a pronounced distortion of the playback signal and a serious loss of signal magnitude. The difficulty in maintaining a reliable tape path is due to the tolerances in the manufacture of tape guides and the tape itself. The tolerances may be in the order of plus or minus two or three thousandths of an inch for each component. A tape guide typically includes a curved element which has a curved surface for guiding the lengthwise travel of the tape and a pair of spaced-apart flat surfaces for guiding the top and bottom edges of the tape. If both flat surfaces of the guide are fixed in a spaced-apart relationship with respect to one another for accommodating a selected nominal tape width, the guide may be too tight or too loose for any particular tape of the nominal width due to the manufacturing tolerances. One of these conditions will cause or allow lateral movement of the tape, the other will cause excessive wear of the tape edge, both will result in an unreliable tape path.
In order to prevent lateral movement of the tape, the prior art provides a fixed guide for one edge of the tape and a resilient guide for the opposite edge of the tape. With this arrangement, the resilient guide is biased against the opposite edge to maintain the one edge in constant engagement with the fixed guide. One prior art resilient tape guide arrangement provides a plurality of elongated springs, one end of each spring being fixed in place and the other end of the spring, which is movable, directly engaging an edge of the tape. Sometimes the movable ends of the springs are provided with ceramic tips so as to reduce wear of the tape and tape guide. Another prior art arrangement is to employ a rigid diaphragm, one end of the diaphragm being pivoted to a fixed base and the other end of the diaphragm being biased against an edge of the tape by a compression spring.
A problem with these aforementioned arrangements, as well as other prior art arrangements, is that unacceptable wear takes place at the edge of the tape which is engaged by the resilient guide. In both of the prior art arrangements the area or areas of contact between the resilient guide and the tape edge are relatively localized. The ceramic tips of the resilient fingers engage the tape edge at a plurality of localized areas while the rigid diaphragm engages the tape edge over a larger but single and less compliant area. The result is wear of the tape and creation of debris which is detrimental to the recording process. However, there is even a more serious problem with the prior art resilient guide arrangements. This is the vibration that is set up in the resilient guide components as the tape travels lengthwise along the curved surface of the tape guide. This is due to the relatively large mass of these components coupled to a spring, and due to the absence of damping. When the moving tape exerts rapid lateral or longitudinal forces on the resilient tape guide, the tape guide responds by vibrating. The vibration of the resilient tape guide components is then transferred back to the tape, resulting in deviation from a nominal tape path and nominal tape velocity. This causes a degradation of recording and playback functions. Therefore, there is a need for a spring-biased tape guide which will maintain a relatively undeviating tape path without effect on velocity and without the generation of debris.